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Dynamic drivers of disease emergence in Africa: From hypothetical frameworks to the field
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Dynamic drivers of disease emergence in Africa: From hypothetical frameworks to the field


Presented by Johanna Lindahl at a Centre of Global Animal Diseases (CGD) seminar, Uppsala, Sweden, 13 December 2013.

Presented by Johanna Lindahl at a Centre of Global Animal Diseases (CGD) seminar, Uppsala, Sweden, 13 December 2013.

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  • 1. Dynamic drivers of disease emergence in Africa: From hypothetical frameworks to the field Johanna Lindahl Presented at a Centre of Global Animal Diseases (CGD) seminar Uppsala, Sweden 13 December 2013
  • 2. What to talk about today? 1. Disease drivers 2. Ecosystem services 3. Proposed frameworks 4. Dynamic drivers of disease in Africa- case studies 5. Discussion
  • 3. The world today • Humans are affecting every part of this planet – Directly or indirectly
  • 4. The world today 7 billion people 1.7 billion overweight/obese 2 billion hidden hunger One billion hungry
  • 5. Livestock is important • 24 billion livestock After rice, second most important source of food 19 billion in developing countries 1 billion poor people depend on livestock 600 million in South Asia 300 million in Sub-Saharan Africa 25% urban
  • 6. Infectious diseases- historically important • In 1918-1920 Spanish flu: • 50- 100 million humans • Late 19th century Rinderpest: • • Early Death of 2/3 of Maasai population in Tanzania and Kenya 19th century Potato blight: • • FAO/G.R. Thomson 25% of Irish population starved or migrated 1967: "…war against infectious diseases has been won“ • US Surgeon General William H. Steward
  • 7. US Surgeon General William H. Steward was wrong Infectious diseases as a cause of death has been decreasing • But not everywhere, and not constant • Increases due to HIV, drug resistance In 2011 55 million died 18 million from infection 7 million deaths in under fives (2/3 infectious)
  • 8. Mortality: global projection, 2004-2030 30 Intentional injuries Other unintentional Road traffic accidents Deaths (millions) 25 20 Other NCD 15 Cancers Cardiovascular diseases 10 Mat//peri/nutritional 5 Other infectious HIV, TB, malaria 0 2004 2015 2030 High-income countries 2004 2015 2030 Middle-income countries 2004 2015 2030 Low-income countries
  • 9. Top Zoonoses (multiple burdens) • Assessed 56 zoonoses from 6 listings: responsible 2.7 billion cases, 2.5 million deaths • Top 13 responsible for 2.2 billion illnesses and most deaths – Wildlife interface – 9 have a major impact on livestock- affect 1 out of 7 – All 13 amenable to on-farm intervention World bank (2010) estimates for last century : • direct costs of zoonotic outbreaks >20 billion USD • indirect costs 200 billion USD
  • 10. Zoonoses Deaths - annual 140000 120000 100000 80000 60000 40000 20000 0
  • 11. Animal health today 5 billion livestock die each year (~20%) Young Adult Annual mortality of African livestock Cattle 22% 6% (About half due to preventable or curable diseases) Shoat 28% 11% Poultry 70% 30% Otte & Chilonda, IAEA
  • 12. Disease emergence? • Definition: – a disease which incidence in humans have been increasing – a disease which has a tendency to spread geographically, cause an increased incidence or infect a new species or new populations – a disease spreading within any host population • Which diseases? • EID twice as likely to be zoonotic than non-zoonotic (zoonotic viruses and protozoa had highest proportion) • Quick mutations • Where? • rapid intensification, increasing interactions between animals, humans and ecosystems, often rapidly changing habits and practices
  • 13. Ecosystem Livestock LH X Humans Disease transmission WH WL Wildlife Spillover event
  • 14. Type of wildlifelivestock-human interface Level of Biodiversity Characteristics of Livestock Population Connectedness between populations Main interface Examples of zoonotic disease with altered dynamics ‘Pristine’ ecosystem with human incursion to harvest wildlife and other resources High No livestock Very low, small populations and limited contact Ignorable WL interface, large WH interface Ebola HIV SARS Nipah virus in Bangladesh and India Ecotones and fragmentation of natural ecosystems farming edges, human incursion to harvest natural resources High but decreasing Few livestock, multiple species, mostly extensive systems Increasing contact between people, livestock and wild animals WH and WL interface dominating, increasing LH Kyasanur Forest disease Bat rabies E. coli interspecies transmission in Uganda Nipah virus in Malaysia Evolving landscape rapid intensification of agriculture and livestock, alongside extensive and backyard farming Low, but increasing peri-domestic wildlife Many, both intensive and genetically homogenous, as well as extensive and genetically diverse High contacts between intensive and extensive livestock, people and peri-domestic wildlife. Less with endangered wildlife. Patchwise large LH interface, decreasing WH and WL Avian influenza Japanese encephalitis virus in Asia Managed landscape islands of intensive farming, highly regulated. Farm land converted to recreational and conservancy Low, but increased number of certain peridomestic wildlife species Many, mainly intensive, genetically homogeneous, biosecure Fewer contacts between livestock and people; increasing contacts with wildlife. Small but increasing WL and WH, decreasing LH Bat-associated viruses in Australia WNV in USA Lyme disease in USA Urban landscape- high densities of humans, with peri-urban intense farming and urban lower intense farming, close to people. Habitat fragmentation of wildlife Low High value animals , mainly small ruminants or pigs, and poultry in the urban centres High densities yield high connectedness Patchwise increasing LH and WH, especially poor areas Plague outbreaks Leptospirosis Dog rabies
  • 15. Ecosystem services – and disease emergence Ecosystem service Importance Effect of decrease Provisioning Economics, livelihoods Increased poverty Regulating Health, environment Increased disease Cultural Well-being, recreation Increased stress? Supporting Basis for the other services Increase in all above
  • 16. Selfactualization Self-esteem and respect Provisioning Love and sense of belonging Safety and security Physiological needs: food, rest, water Hierarchy of needs according to Maslow.
  • 17. Livestock Land use changes Land degradation Wildlife Biodiversity Vectors Socio-economics Provisioning services Regulating services Infections Lack of energy Lack of nutrients Nutrition Health Too much energy Stress Cultural services Physical and chemical Pollution Climate
  • 18. Basic epidemiological principles • For an outbreak to occur: R0 > 1 • SIR model Susceptibles Susceptibles Infectious Exposed Removed Infectious Removed
  • 19. Global trade and travelling Environmental land degradation Civil unrest Urbanization Poverty Markets Migration of people or animals to new areas Close contact between different species New habits, new cultures New population at risk Transfer or recruitment of new vectors Increased contact with wildlife New species at risk / host transfer Increased number of susceptible Governmental finances and priorities Undernutrition, starvation Ageing population Decreased immunization and immunity
  • 20. Agricultural intensification and development Deforestation Irrigation Fertilisers Littering Habitat fragmentation Disrupted social systems Industrialization of animal production Poverty Lack of knowledge Decreased biodiversity Less dilution from alternate hosts Increased number of vectors Climate changes Markets Water scarcity Reduced food safety Increased risk of exposure Urbanization High density
  • 21. Destroyed agricultural land, soil degradation War, migration Water scarcity Lack of knowledge Poverty Increased incidence of HIV Pollution Disrupted social systems Lack of fundings Starvation, malnutrition Ageing population Compromised immune system Excess, incorrect use of antibiotics and antivirals Remote areas Inadequate health systems Increased infectivity Pathogen evolution Resistant pathogens
  • 22. Irrigation Education Urbanization Increased animal production Improved nutrition Improved infrastructure Global trade Immunization programs Adequate health systems Access to medicines Removed/recovered
  • 23. Anthropogenic action: Increased irrigation Effect on ecosystem: Creates more larval habitats Possible consequence: More infected vectors Epidemiologic consequence: More individuals exposed Increased disease • This step requires the presence of a vector-borne pathogen and the presence of competent vectors
  • 24. One action- multiple results Deforestation Decreased biodiversity Changed vector habitats Habitat fragmentation Increased disease transmission (where biodiversity would cause a dilution effect) Reduced disease transmission (where biodiversity would cause an amplification effect) Increased vector populations Decreased vector populations Increased edge effects and interfaces between humans, domestic animals and wildlife Increased animal densities and contact rates Example: Some vectorborne diseases, such as Lyme disease Example: Parasites in greater apes which are favoured by host richness Example: Deforestation give more agricultural land, more irrigation and more Japanese encephalitis virus increase Example: Malaria decrease after deforestation in Thailand Example: Habitat destruction and forrest encroachment were drivers between Nipah virus otbreaks Example: Increased parasite burdens in wildlife
  • 25. One action- multiple results Agricultural industrialization Improved veterinary care Intensification Extensification Increase use of antibiotics Eradication of animal diseases Higher animal densities Higher biosecurity Trends of ecologic production with outdoor animals Eradication of rinderpestbetter cattle production Decrease of bacterial diseases in animals Increase risk of drug resistant pathogens Eradication of Samonella pullorum- better poultry production but increased Salmonella enterica High propagation of infectious diseases, such as avian influnza Backyard poultry Decreased risk of introduction of disease Low biosecurity and low animal density More natural behaviour could give less stress and increase animal welfare Increased infectious diseases such as Toxoplasma gondii
  • 26. Dynamic drivers of disease in Africa How does changes in land use and anthropogenic changes affect diseases? And how do we study it?
  • 27. DDDAC
  • 28. Case study: Zambia/ Zimbabwe • Trypanosomiasis/tse-tse • Land use changes – Protected area – Area where livestock has been increasing – Former large-scale farms with low biodiversity
  • 29. Case study: Ghana • Henipa virus/ bats • Urban –rural migration • Livelihoods, poverty, ecology and the association with disease – How do humans interact with bats and what perceptions do they have of the risks – Protected/sacred area – Urban area
  • 30. Case study: Sierra Leone • Lassa fever/ multimammate rats • Land use changes and rodent ecology – Urban-rural – Irrigation and precipitation – Human-rat interaction and risk perceptions
  • 31. Case study: Kenya • Rift valley fever/ mosquitoes • Land use changes – Protected area vs irrigated area – Pastoralist areas
  • 32. Case study: Kenya • Rift valley fever/ mosquitoes • Land use changes – Protected area vs irrigated area – Pastoralist areas
  • 33. Case study: Kenya • Making changes in a highly diverse landscape • Increased number of scavengers • Increased numbers of mosquitoes
  • 34. Case study: Kenya • Participatory rural appraisals indicated a concern about rodents
  • 35. Case study: Kenya • What to study: – Can we trust hospital data? – Screen all febrile patients – Too many differentials: Malaria, RVF, Dengue, YF, Brucella, Leptospira, Chikungunya, CCHF
  • 36. Case study: Kenya • Who to study: – Humans and livestock – Mosquitoes – Rodents – Ticks? – Baboons?
  • 37. Cross-cutting issues • Participatory rural appraisals • The economic burden of disease • The association between poverty and zoonosesthe vicious circle • Climate change and predictive modelling
  • 38. The perfect model? Ecosystem health Animal health Human health
  • 39. Far from perfect Elephants or mosquitoes ? • Assessing biodiversity Assets or knowledge? • Assessing poverty • Assessing human- animal interactions • Assessing impact Compared to everything else? • Finding mitigations Food or animal contact?
  • 40. Not the end…. ….but the beginning Open to questions Open to discussion
  • 41. Agriculture Associated Diseases http://aghealth.wordpress.com/ This work, Dynamic Drivers of Disease in Africa Consortium, NERC project no. NE-J001570-1, was funded with support from the Ecosystem Services for Poverty Alleviation (ESPA) programme. The ESPA programme is funded by the Department for International Development (DFID), the Economic and Social Research Council (ESRC) and the Natural Environment Research Council (NERC).
  • 42. better lives through livestock ilri.org The presentation has a Creative Commons licence. You are free to re-use or distribute this work, provided credit is given to ILRI.